WASHINGTON (CNN) -- Al Qaeda is increasing its efforts to get operatives into the United States for an attack and has nearly all the resources it needs to carry out such a mission, a draft of a new U.S. government intelligence analysis says, according to two government officials familiar with it.

A Pakistani soldier patrols an al Qaeda stronghold near the Afghan border.

Those resources include a safe haven along the Pakistan-Afghanistan border from which the terrorist organization's leaders can operate, the officials told CNN.

The classified report, called a National Intelligence Estimate, represents the combined analyses of all 16 U.S. intelligence agencies. Officials spoke to CNN anonymously because the report is not final.

On Wednesday, a senior government official told CNN about another analysis, prepared for senior U.S. policymakers, that concludes al Qaeda is the strongest it has been since the aftermath of the September 11, 2001, terrorist attacks, despite more than five years of military actions and counterterrorism operations by the United States and its allies.

That analysis also dealt with the issue of al Qaeda's resurgence in the tribal areas of Pakistan, where Pakistani President Pervez Musharraf last year gave primary responsibility for controlling the border areas between Pakistan and Afghanistan to tribal leaders.

The United States considers Musharraf an ally in the fight against al Qaeda and has been reluctant to pressure him to do more to control the border areas, where authorities believe both al Qaeda and the Taliban, vanquished from Afghanistan, have regrouped.

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Musharraf has repeatedly said his government is working hard to curb terrorists and extremists in its territories.

The NIE draft report expresses concern about the possibility of a growing number of extremists who may already be in the United States, the two officials said, and that al Qaeda is still in pursuit of chemical, biological, and nuclear weapons.

The Associated Press first reported details of the draft NIE's contents.

To prevent an attack, a priority for the FBI and other intelligence agencies is to run down any leads about potential sleeper cells in, or on their way to, the United States, and about the radicalization of U.S. residents.

Homeland Security Secretary Michael Chertoff has repeatedly warned of concerns al Qaeda is trying to get operatives into the United States through one of several European countries whose residents do not require a visa to enter the United States. All visitors to the United States, however, must show a valid passport.

The office of the Director of National Intelligence, which is responsible for putting together the report, refused comment on its contents. A spokesman for that office said the report has been in the works for two years and much of its content has been reflected in congressional testimony and other public statements.

A declassified version of the report is expected to be released soon, according to the two officials.E-mail to a friend